1. Field of the Invention
The present invention relates to a radiation shadow indicator, and more particularly to an indicator which is positioned at a point on the earth for acquiring an indication of objects which cast shadows on the point at any selected time of year and day.
2. Description of the Prior Art
When installing a solar energy system it is essential to select a site for a solar energy collector which will receive as much solar radiation as possible, especially at the hours and/or seasons where the solar energy is most required. In order to determine the amount of solar energy that will be available at a potential site it is, of course, necessary to consider shadows cast on the site by terrestrial objects during annual as well as diurnal periods.
The existing method for accurately determining shadowing of a solar energy collector site from solar radiation in relation to annual and diurnal periods is, essentially, to prepare a shade mask, or diagram of those objects seen from the site against the sky, and then to combine this shade mask with a diagram to the same scale thus to form a composite diagram showing the path of the sun at the site for the various days of the year. The hour and the dates when the shadows occur are then read from the composite diagram. This graphical method requires not only that information be obtained in the field for the shadow mask, but also requires preparation of both a shade mask and a solar path diagram, and, finally, that these diagrams be combined before a desired reading of times and dates when shadows are cast on a proposed collector site can be made. It is, of course, necessary to repeat these procedures for each potential solar energy collector site under consideration.
This method, obviously, is relatively complex and time consuming. In addition, the graphical procedures aforedescribed require persons having special skill and training in their performance. As a result of these factors, the present method for determining the effect of shadowing by terrestrial objects on a solar energy system is relatively expensive and time consuming.
It is, therefore, the general purpose of the instant invention to provide a simple and economic method and device for use by relatively unskilled personnel in rapidly predicting periods of terrestrial object occlusion of a moving source of celestial radiation at proposed energy collector sites.